Metallophthalocyanines linked to organic copolymers as efficient oxidative supported catalysts

Article abstract of DOI:10.1002/1099-0682(200107)2001:7<1775::AID-EJIC1775>3.0.CO;2-1

The covalent anchoring of metallo(chlorosulfonyl)phthalocyanines 1 onto the acrylic copolymers 2 and 3 has been achieved. When using H₂O₂ or KHSO₅ as oxidant, these supported catalysts are able to oxidize a poorly biodegradable molecule such as 2,4,6-trichlorophenol or a tannin model such as 3,5-di-tert-butylcatechol. The influence of the spacer and the nature of the reaction medium on the catalytic activities have been studied, as well as the recycling of these supported metallophthalocyanine catalysts.

Full text of DOI:10.1002/1099-0682(200107)2001:7<1775::AID-EJIC1775>3.0.CO;2-1

FULL PAPER
Metallophthalocyanines Linked to Organic Copolymers as Efficient Oxidative
Supported Catalysts
Muriel Sanchez,[a] Nicolas Chap,[a] Jean-Bernard Cazaux,[b] and Bernard Meunier*[a]
Keywords: Phthalocyanines / Supported catalysts / Polymers / Oxidations
The covalent anchoring of metallo(chlorosulfonyl)phthalocy-
such as 3,5-di-tert-butylcatechol. The influence of the spacer
anines 1 onto the acrylic copolymers 2 and 3 has been and the nature of the reaction medium on the catalytic activ-
achieved. When using H2O2 or KHSO5 as oxidant, these sup-
ported catalysts are able to oxidize a poorly biodegradable
molecule such as 2,4,6-trichlorophenol or a tannin model
ities have been studied, as well as the recycling of these sup-
ported metallophthalocyanine catalysts.
Introduction
chols, and polycondensed aromatics.[7] One limitation of
these catalysts is the formation in solution of inactive ag-
gregates and dimers of the metallophthalocyanine com-
plexes, which significantly affects their catalytic properties.
This aggregation phenomenon is usually depicted as a co-
planar association of the aromatic rings driven by enhanced
van der Waals forces and dimer formation through µ-oxo
bridges.[7a,8] In solution, the monomerization of water-sol-
uble metallophthalocyanines can be achieved by adding an
organic co-solvent[7a] or a detergent.[9] Another strategy
used to obtain a monomolecular dispersion of these macro-
cyclic complexes is based upon their heterogenization on
the surface of a support. Several types of carrier have been
used for this task, such as charcoal,[10] organic polymers,[11]
silica,[12] zeolites,[13] and clays.[14] Among the advantages of
using supported catalysts is the easy separation of the cata-
lysts from products and the subsequent possible recycling
of the catalyst.[15]
Metallophthalocyanines (e.g., 1 and 4, Scheme 1) have at-
tracted considerable interest because of their structural sim-
ilarity to metalloporphyrin complexes found at the active
sites of metalloenzymes.[1] These phthalocyanine complexes
are often more easily prepared than synthetic metallopor-
phyrins, and exhibit interesting properties in areas such as
sensitizers[1,2] (e.g., in photodynamic cancer therapy), cata-
lysts[1,3] (e.g., for thiol oxidation in gasoline fractions), elec-
trocatalysts[1,4] (e.g., for O2 reduction in fuel cells),
sensors[1][3c,5] (e.g., NOx and O2 gas sensors) or nonlinear
optical devices.[1,6]
Recently, we have described the covalent attachment of
the chlorosulfonyl-substituted iron-phthalocyanine 1a
(Scheme 1) to functionalized 3-aminopropyl-silica via a sul-
fonamide linkage.[16] This supported catalyst, when using
hydrogen peroxide as oxidant, is able to degrade a recalcit-
rant pollutant. However, the efficiency of this catalytic sys-
tem was lower than that obtained under homogeneous con-
ditions. This probably results from diffusion-limitation ef-
fects inherent to the use of silica as support, despite the fact
that mineral supports have a better reputation of chemical
stability compared to organic polymers in catalytic oxida-
tions with supported catalysts.[17]
Scheme 1. Structure of the metallo[2,9,16,23-tetrakis(chloro-
sulfonyl) and -tetrasulfo]phthalocyanines 1 and 4
In the field of bio-inspired oxidations, it has been shown
in our laboratory that water-soluble metallo(sulfo)phthalo-
cyanines 4 (Scheme 1) can be used as oxidation catalysts
with H2O2 or KHSO5.[7] Highly reactive metalϪperoxo
(e.g., FeIIIϪOOY) and metalϪoxo (FeIVϭO) species are
probably involved in the catalytic oxidations of poorly bio-
degradable molecules such as polychlorinated phenols, cate-
Here, we report the preparation of new organic polymers-
supported metallophthalocyanines, and their efficiency as
oxidation catalysts.
Results and Discussion
[a]
Laboratoire de Chimie de Coordination du CNRS,
Preparation of the Supported Catalysts
205 route de Narbonne, 31077 Toulouse cedex 4, France
E-mail: bmeunier@lcc-toulouse.fr
We have previously shown that a sulfonamide linkage
used to immobilize an iron-phthalocyanine onto modified
[b]
EXPANSIA,
Route d’Avignon, BP N 6, 30390 Aramon, France
Eur. J. Inorg. Chem. 2001, 1775Ϫ1783
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0707Ϫ1775 $ 17.50ϩ.50/0
1775

M. Sanchez, N. Chap, J.-B. Cazaux, B. Meunier
FULL PAPER
silica is stable under oxidative conditions.[15] Therefore, we
The immobilization of the chlorosulfonyl derivatives 1 of
decided to use the same type of linkage for the attachment the iron- and cobalt-phthalocyanines was achieved by heat-
of chlorosulfonyl-substituted phthalocyanine complexes 1 ing a mixture of resin and complex in pyridine to reflux.
onto organic supports. The organic supports used were the The supported catalysts FePc-SO2NH-Met-Expansin (9)
acrylic copolymers Met-Expansin-NH2 (2) and Met-Ex- (20.0 µmol of iron per gram of dry resin), FePc-SO2N(pip)-
pansin-Piperazine (3), which both possess an amino-func- Met-Expansin (10a) (26.5 µmol Fe/g), and CoPc-SO2N-
tionalized pendant arm and were prepared from Met-Ex- (pip)-Met-Expansin (10b) (42.0 µmol Co/g) were thus ob-
pansin (5) by EXPANSIA. These resins were synthesized tained from the polyacrylamides 2 and 3 (Scheme 4).
from the polymerization of the monomer N-acryloylpyrroli-
After filtration, the loading of the supports was indirectly
dine (6), the cross-linking agent N,NЈ-bis(methacryloyl)-1,2- calculated by determining the amount of 1 remaining in
diaminoethane (7), and N-acryloyl-β-alanine methyl ester solution by UV/Vis spectroscopy. No release of metalloph-
(8) as functionalizing agent (Patent EP 79842, 1982) thalocyanine was observed after several washings with
(Scheme 2).
water, dimethylformamide, and ethanol. The green color of
these modified polymers obtained after the washing proced-
ures strongly suggested that the metallophthalocyanine
complexes were attached in monomeric form (µ-oxo-metal-
lophthalocyanine dimers and aggregates are generally
blue).[7a] It is important to note that no desorption of the
metallophthalocyanine catalysts was detected under oxidat-
ive conditions (e.g., after addition of H2O2 or KHSO5) ac-
cording to UV/Visible measurements.
For comparison, the silica-supported catalysts FePc-
SO2NH-Silica (11) (42.0 µmol Fe/g) and FePc-SO2N(pip)-
Silica (12) (40.0 µmol Fe/g) were also prepared. The grafted
polymer 11 comes from the direct fixation of 1 onto a com-
mercially available modified silica featuring primary amine
linkers, whereas 12 contains the piperazine spacer intro-
duced by the same procedure used for the preparation of 3
from 2 (Scheme 5).
Scheme 2. Synthesis of Met-Expansin (5)
The polyacrylamide 5 can be treated with ethylenediam-
ine to afford 2 (Patent EP 81408, 1982) (Scheme 3). This
resin contains 0.56 mmol-equiv. of NH2 per gram of dry
material that can be used to covalently anchor the metal-
lo(chlorosulfonyl)phthalocyanines 1. A spacer can also be
used to increase the distance between the catalyst and the
polymer surface. This modification of the tether helps to
increase the solvent, substrate, and oxidant access, similar
to homogeneous reaction conditions. Copolymer 3 was pre-
pared by treating 2 with bromoacetic anhydride, followed
by the addition of piperazine (Patent Fr. Dem. 9904135,
1999). It contains 0.5 mmol-equiv. of terminal NH func-
tions per gram of dry resin.
Catalytic Activities of the Grafted Complexes 9؊11 for the
H2O2 Oxidation of a Chlorinated Pollutant
2,4,6-Trichlorophenol (TCP) is produced by paper mills
during the oxidative chlorine degradation of lignin in white
paper manufacturing.[18] Due to its slow biodegradation by
aerobic or anaerobic microorganisms and its resistance to
oxidative or reductive chemical treatments, this substrate is
extremely persistent in the environment. Thus, TCP is com-
monly used as a pollutant model. It has been shown that
ligninase (a peroxidase isolated from the white-rot fungus
Phanerochaete chrysosporium) is able to degrade TCP by
an oxidative pathway, although the conversion is slow.[18b]
Synthetic metalloporphyrins, which are efficient peroxidase
models, are able to oxidize TCP to the corresponding qui-
none, but are unable to cleave the aromatic ring of TCP.[19]
Using either soluble metallophthalocyanines, or the corres-
ponding immobilized catalysts onto a support (silica or
Amberlite), with H2O2 as a ‘‘green’’ oxidant, TCP has been
converted in two classes of compounds: aromatic ring cleav-
age products (C4 diacids, with chloromaleic acid being the
major product) and oxidative coupling products
Scheme 3. Synthesis of Met-Expansin-NH2 (2) and Met-Expan-
sin-Piperazine (3)
The two organic copolymers 2 and 3 are insoluble in or- (Scheme 6).[7,20]
ganic solvents and in aqueous media; however, these resins
Under the same experimental conditions [1 m TCP so-
swell in protic solvents to form gels. This property is cer- lution in a mixture of 50 m phosphate buffer (pH ϭ 7)/
tainly important for the preparation of supported catalysts, acetone (80:20), 6 m H2O2, and 2 mol-% of catalyst], how-
because the surface area of the carrier is considerably in- ever, the reaction was markedly faster with the iron-tetrasul-
creased making the active catalytic centers more accessible. fophthalocyanine catalyst 4b under homogeneous condi-
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Eur. J. Inorg. Chem. 2001, 1775Ϫ1783

Metallophthalocyanines Linked to Organic Copolymers as Efficient Oxidative Supported Catalysts
FULL PAPER
Scheme 4. Immobilization of the metallophthalocyanines 1 onto 2 and 3
organic co-solvent, the supported iron catalysts 9 and 10a
with H2O2 were able to degrade 85% (Run 4) and 62% (Run
10) of the TCP, respectively, within 1 h. The presence of an
organic co-solvent such as ethanol or acetone, which al-
lowed a better solubilization of the poorly water-soluble
TCP substrate, improved the degradation process up to full
conversion of TCP within 1 h (Runs 5, 6, 11, and 12). Also,
with acetone as co-solvent, the degradation of TCP was
complete after 20 min with 9 and after 25 min with 10a.
The turnover rates (based on the first 30 min of the reac-
tion) of these two supported catalysts are 150 and 120
cycles per hour, respectively. These results are of great inter-
est, since the catalytic activities of these new supported
metallophthalocyanines are comparable to those observed
under homogeneous conditions.
The recycling of 10a, a key point for supported catalysts,
was then investigated. After a first catalytic oxidation, a
second portion of pollutant and oxidant was added to the
reaction mixture. In this second run, 91% of TCP was con-
verted in 15 min (Run 13) indicating that the catalytic activ-
ity of the metallophthalocyanine remained intact.
Scheme 5. Immobilization of the metallophthalocyanines 1 onto
silica
tions, compared to the iron complex 11 grafted onto silica
modified with primary amine linkers. Indeed, full conver-
sion of TCP was achieved within 45 min with 4b (Run 2,
Table 1), while it took 1 h for the supported catalyst 11 to
oxidize only 52% of TCP (Run 3).
For comparison, the catalytic activity of the supported
cobalt complex 10b was also checked (Runs 14Ϫ17). The
The oxidative properties of the metallophthalocyanines full conversion of TCP could be achieved in 30 min with 4
immobilized onto the organic polymers 2 and 3 were also mol-% of 10b and with 20% of acetone in the reaction mix-
investigated. First, we checked that the TCP substrate was ture (Run 17). Although the results obtained with this sup-
not oxidized by H2O2 and the support material alone, in ported catalyst are less impressive than with the corres-
the absence of metallophthalocyanine catalyst (Run 1). In ponding iron(III) complex, they are also of potential com-
addition, this control experiment confirmed that there is no mercial interest. Indeed, the (chlorosulfonyl)phthalocyanine
physisorption of the substrate onto the surface of the sup- 1b used for the immobilization on the organic copolymer
port. In the presence of phosphate buffer, but without any was synthesized from the readily available sulfo precursor
Eur. J. Inorg. Chem. 2001, 1775Ϫ1783
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M. Sanchez, N. Chap, J.-B. Cazaux, B. Meunier
FULL PAPER
Scheme 6. Degradation products of 2,4,6-trichlorophenol by the catalytic metallophthalocyanine/H2O2 systems
Table 1. Oxidation of 2,4,6-trichlorophenol (TCP) catalyzed by the metallophthalocyanines/H2O2 systems
Run
Catalyst
Cat./TCP
[mol-%]
Solvent
TCP conversion (%)
1 h
T.O.[a]
1:2 h
2 h
[hϪ1
]
1
2
3
4
5
6
7
8
Ϫ
4b
11
9
Ϫ
2
2
2
2
2
2
3
3
2
2
2
2
PB[b]
PB/acetone
PB/acetone
PB
PB/EtOH
PB/acetone
H2O/NaOH
H2O/NaOH
H2O/NaOH
PB
PB/EtOH
PB/acetone
PB/acetone
7
94
39
74
84
100
43
53
71
Ϫ
99
100
Ϫ
100
52
85
100
Ϫ
Ϫ
94
39
74
84
Ͼ 100
43
69
88
9
9
9
55
65
89
62
100
56
79
93
67
9
35
47
9[c]
10
11
12
13
9
10a
10a
10a
10a
Ͻ 62
99
Ͼ 100
Ͼ 100
Ͼ 100
38
23.5
33.5
50
100
91[d] (15 min)
14
15
16
17
18
19
10b
10b
10b
10b
12
2
4
4
4
2
2
PB
PB
38
47
67
100
91
9
46
57
94
44
58
100
PB/EtOH
PB/acetone
PB/acetone
H2O/NaOH
100
11
91
9
12
12
[a]
[b]
[c]
T.O.: Turn over numbers calculated after 30 min of reaction. Ϫ PB: Phosphate buffer (pH ϭ 7). Ϫ Sequential addition of H2O2:
[d]
4 ϫ 1 aliquot every 10 min. Ϫ
Recycling of the supported catalyst: after 15 min of a first oxidation reaction, new portions of TCP
and H2O2 were added in the same batch.
4c, which is widely used in the industrial mercaptan oxida- the distance between the catalyst and the support is rather
tion process (Merox) for the treatment of petroleum distil- limited. In contrast, with a more rigid carrier material like
lates.[3]
silica, this modification could notably change the catalytic
The covalent attachment of the metallophthalocyanines properties of a metallophthalocyanine complex covalently
1 onto the organic copolymers 2 and 3 proved to be suitable linked to silica. In order to verify this hypothesis, we deter-
for the preparation of active systems for the catalytic oxid- mined the oxidative properties of the silica-supported iron
ative degradation of recalcitrant pollutants such as 2,4,6- complex 12, which features the same piperazine spacer as
trichlorophenol. The different properties (flexibility, swell- in 10a.
ing, etc.) of these carriers make them excellent candidates
for catalytic supports.
Influence of the Piperazine Spacer
It should be noted that the behavior of 9 and 10a are
In order to determine the influence of the spacer, we
almost identical, with 9 being only slightly more efficient compared the oxidative properties of 12 (containing
than the corresponding piperazine-containing polymer. 40.0 µmol of iron per gram of resin) to those of 11 with the
These organic copolymers 2 and 3 are relatively flexible, same catalyst loading (42.0 µmol/g). In the oxidative de-
consequently the role of an additional spacer to increase gradation of TCP with H2O2, the catalytic activity of the
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Eur. J. Inorg. Chem. 2001, 1775Ϫ1783

Metallophthalocyanines Linked to Organic Copolymers as Efficient Oxidative Supported Catalysts
FULL PAPER
supported catalyst containing the piperazine spacer was 3 BaeyerϪVilliger oxidations.[23] An initial control experi-
times higher after 30 min (Runs 3 and 18, Table 1). In addi- ment was made to ensure that TCP was not oxidized by
tion, for the first time, it was possible to achieve a full con- KHSO5 without catalyst (Run 1, Table 2) and that there
version of TCP in 1 h with a metallophthalocyanine grafted was no leaching of the iron-phthalocyanine under these new
onto modified silica (Run 18). This result strongly indicates oxidation conditions [8 mg of 9 suspended in 8 mL of a
that when anchoring a large catalyst molecule like a metal- phosphate buffer (pH ϭ7) with 5 equiv. of KHSO5].
lophthalocyanine (a macrocyclic molecule with a diameter of
In a purely aqueous medium, the degradation of TCP by
˚
ca. 25 A) onto a rigid support such as silica, it is necessary the catalytic 9 (2 mol-%)/KHSO5 system is very fast (79%
to introduce a long spacer between the catalyst and the sur- in 5 min, Run 2, Table 2). However, the conversion of TCP
face of the support. Without this modification, the oxidative reached a plateau after 10 min and a bleaching of the sup-
activities of the corresponding supported catalysts are re- ported catalyst was observed. The pH measurement of the
duced. These results provide further motivation to use the solution gave a value of 2.5, which was attributed to the
flexible organic copolymers 2 and 3 as supports in cata- intrinsic acidity of KHSO5. At such a low pH value, the
lytic oxidations.
supported catalyst is probably decomposed. In contrast,
when the reaction mixture was buffered at pH ϭ 7 using a
phosphate buffer, the conversion of TCP was complete in 5
min (Run 3). Under these conditions, the turnover rate of
this supported iron-(sulfonamido)phthalocyanine was 10
catalytic cycles per minute (based on the first five minutes
of the reaction). With the catalytic 9/KHSO5 system, the
turnover rate can be increased up to 16 cycles/min using 1
mol-% of catalyst (Run 4). In contrast, with only 0.1 mol-
% of catalyst, the degradation of TCP was incomplete after
1 h (Run 5).
We also checked the possibility of recycling this sup-
ported catalyst under these strong oxidation conditions.
After a first catalytic reaction, new portions of substrate
and oxidant were added every 5 min (Run 6). The results
were very surprising: the catalytic system was still efficient
after the addition of 3 new portions of pollutant and had
retained its initial catalytic activity.
We have established that the activation of metallophthalo-
cyanines anchored onto 2 and 3 with either hydrogen per-
oxide or potassium monopersulfate as oxidants is an effici-
ent method for the oxidative degradation of a notable pol-
lutant such as TCP. Moreover, NMR studies carried out
after the catalytic oxidation of TCP with H2O2 (as well as
with KHSO5) have shown the formation of ring cleavage
products, which are biodegradable. For example, for the
H2O2 oxidation of TCP catalyzed by 10a, we observed the
formation of 12% of chloromaleic acid, 3% of chlorofum-
aric acid, 4% of maleic acid, 3% of fumaric acid and 6% of
coupling products. Thus, these catalytic systems might be
useful for the oxidative treatment of industrial waste waters.
However, these bio-inspired supported oxidative catalysts
might also be useful as bleaching agents in a new generation
of washing powders, able to operate at room temperature.
Catalytic Oxidation of TCP in Pure Aqueous Medium
(without Buffer)
The experiments described above for the degradation of
TCP were carried out in phosphate buffer (pH ϭ 7) me-
dium. Under homogeneous conditions it has been shown
that this pH value is optimal for a good catalytic activity.
This can be explained by the fact that the first step of TCP
degradation is a one-electron oxidation of the phenolate an-
[7a]
ion
(pKa value of TCP: 6.2).[21] However, since the final
aim of this work is the decontamination of industrial waste
waters, the presence of phosphate ions is ecologically not
appropriate.
With this in mind, we tried to degrade TCP in a pure
aqueous medium, using the most active polyacrylamide-
and silica-supported catalysts 9 and 12. The pH value of
the reaction mixture was adjusted to 7 with sodium hydrox-
ide in order to have only the more oxidizable phenolate
form of the substrate in solution. With a 2 mol-% ratio
catalyst/TCP, the supported catalyst 9 and H2O2 are able to
oxidize 55% of the starting TCP after 1 h (Run 7, Table 1),
whereas, under the same conditions, the iron-phthalocyan-
ine grafted onto the modified piperazine-silica 12 converted
only 11% of TCP (Run 19). Since the tetrasulfophthalocy-
anine 4b is totally inactive in a purely aqueous medium un-
der homogeneous conditions,[22] these results were encour-
aging. The ratio catalyst/substrate was raised to 3 mol-% for
9 and the conversion of TCP increased to 65% after 1 h and
to 79% after 2 h (Run 8). With a sequential addition of
the oxidant in 4 aliquots, every 10 min, a quasi-complete
degradation of TCP can be achieved in a purely aqueous
medium within 2 h (Run 9). The sequential addition of
H2O2 disfavors its consumption by a disproportionation re-
action (leading to water and molecular oxygen) induced by
the catalase-like reactivity of the metallophthalocyanine
complex.[7a]
H2O2 Oxidative Degradation of 3,5-Di-tert-butylcatechol
Catalyzed by 9
Catechol and its derivatives are often used as substrates
for the evaluation of bleaching agents since they are consid-
ered good models of stains (catechols are the most common
Catalytic Degradation of TCP with KHSO5 as Oxidant
Potassium monopersulfate (KHSO5) is an oxygen atom structure encountered in condensed tannins, which are
donor that has been shown to be highly efficient for the among the main stains).[24] Under homogeneous condi-
activation of metallophthalocyanines and metalloporphyr- tions, the iron-sulfophthalocyanine 4b in conjunction with
ins.[7,19] It is commercially available as the triple salt an oxidant was able to degrade several catechols such as
2KHSO5·KHSO4·K2SO4, and is
a
classic reagent in catechol itself, as well as its 3-methyl, 3-methoxy, 3,5-di-
Eur. J. Inorg. Chem. 2001, 1775Ϫ1783
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M. Sanchez, N. Chap, J.-B. Cazaux, B. Meunier
FULL PAPER
Table 2. KHSO5 oxidation of 2,4,6-trichlorophenol (TCP) catalyzed by 9
Run
Cat./TCP
[mol-%]
Solvent
TCP conversion (%)
T.O.[a]
5 min
10 min
15 min
30 min
60 min
[minϪ1
]
1
2
3
Ϫ
2
2
1
0.1
2
PB[b]
H2O[c]
PB
PB
PB
Ϫ
79
100
81
36
61
97
94
87
Ϫ
88
Ϫ
89
0
92
Ϫ
92
Ϫ
7.9
10
16.2
72
6.1
9.7
9.4
8.7
4
96
45
5
53
66
72
6[d]
PB
[a]
[b]
[c]
[d]
T.O.: Turn over numbers calculated after 5 min. Ϫ
PB: Phosphate buffer (pH ϭ 7). Ϫ Pure aqueous media (pH ϭ 2.5). Ϫ
Recycling of the supported catalyst: after 5 min of a first oxidation reaction with 3.75 equiv. of KHSO5, new portions of TCP and
KHSO5 were added every 5 min in the same batch.
tert-butyl, and tetrachloro derivatives.[25] The degradation solubility of DTBC. With 2 mol-% of catalyst, the results
products from 3,5-di-tert-butylcatechol (DTBC) were iden- for the degradation of DTBC are quite similar in the three
tified by 1H NMR as 3,5-di-tert-butyl-1,2-benzoquinone, different reaction media (Runs 2Ϫ4, Table 3). The most in-
3,5-di-tert-butylmuconic anhydride, and 3,5-di-tert-butyl-5- teresting results were obtained without buffering the reac-
(carboxyhydroxymethyl)-2-furanone (Scheme 7).
tion solution (which can be considered as an advantage),
and as a result, attempts were made to optimize this reac-
tion. By increasing the catalyst/substrate ratio to 3 mol-%,
full conversion of DTBC was achieved in 1 h (Run 5,
1
Table 3). H NMR studies carried out after the catalytic
oxidation of DTBC in a water/acetonitrile mixture revealed
the formation of 3,5-di-tert-butyl-1,2-benzoquinone (50%
yield, no other products could be detected).
Scheme 7. Degradation products of 3,5-di-tert-butylcatechol cata-
lyzed by the iron-tetrasulfophthalocyanine 4b
The recycling capacity of 9 was also studied in the de-
When H2O2 was used as oxidant, the noncatalyzed reac- gradation of DTBC. In this case, this supported catalyst
tion with DTBC was negligible (Run 1, Table 3). The oxid- also showed excellent behavior without loss of its oxidative
ative properties of the 9/H2O2 system were used for the properties, as expected for an efficient long-life catalyst. In
catalytic degradation of DTBC. We first noted that the sub- fact, after having converted 82% of DTBC in a first cata-
strate was not physisorbed on the surface of the support. lytic oxidation, the same system was still able to degrade 4
Three reaction media were then checked for the degradation new portions of substrate (Run 6, Table 3). However, for an
of DTBC at room temperature: borate buffer (pH ϭ 9)/ application in washing powders, it would be accurate and
CH3CN (50:50, v/v), phosphate buffer (pH ϭ 7)/CH3CN realistic to work with a water-soluble catechol such as 3,4-
(50:50, v/v) and H2O/CH3CN (50:50, v/v). The presence of dihydroxybenzoic acid, current work is underway in this
acetonitrile is necessary as organic co-solvent for a good direction.
Table 3. H2O2 oxidation of 3,5-di-tert-butylcatechol (DTBC) catalyzed by 9
Run
Solvent
pH
Cat./DTBC
[mol-%]
TCP conversion (%)
30 min
T.O.[a]
10 min
20 min
45 min
60 min
[hϪ1
]
1[b]
2
3
H2O/CH3CN
BB/CH3CN[c]
PB/CH3CN[d]
H2O/CH3CN
H2O/CH3CN
H2O/CH3CN
5.5
9
7
5.5
5.5
5.5
Ϫ
2
2
2
3
Ϫ
23
41
29
39
Ϫ
36
49
45
71
1
Ϫ
68
60
71
90
2
Ϫ
61
55
61
56
55
49
47
37
61
55
61
84
82
74
70
55
78
62
81
97
4
5
6[e]
3
71
78
[a]
[b]
[c]
[d]
T.O.: Turn over numbers calculated after 30 min. Ϫ Control reaction without catalyst. Ϫ BB: Borate buffer (pH ϭ 9). Ϫ
PB:
[e]
Phosphate buffer (pH ϭ 7). Ϫ Recycling of the supported catalyst: after 30 min of a first oxidation reaction, new portions of TCP
and KHSO5 were added every 30 min in the same batch.
1780
Eur. J. Inorg. Chem. 2001, 1775Ϫ1783

Metallophthalocyanines Linked to Organic Copolymers as Efficient Oxidative Supported Catalysts
FULL PAPER
12 h at 50 °C. A suspension of the carrier containing CH2Br end
groups in DMF (5 mL) was added to a solution of piperazine
(0.77 g, 9.00 mmol) in DMF (5 mL) and stirred 24 h at room tem-
perature. The modified support thus obtained was isolated by fil-
tration, washed three times with water (3 ϫ 20 mL), ethanol (3 ϫ
20 mL) and acetone (3 ϫ 20 mL) prior to drying at 50 °C for 12 h.
Yield: 0.78 g (78%).
Conclusion
The covalent anchoring of metallophthalocyanines onto
the acrylic copolymers Met-Expansin-NH2 (2) and Met-
Expansin-Piperazine (3) allowed the fixation of these mac-
rocyclic complexes in a monomolecular dispersion, resistant
to oxidative conditions. These bio-inspired supported cata-
lysts, when activated with H2O2 (the ‘‘green’’ oxidant) or
KHSO5 were able to fully degrade a recalcitrant pollutant
such as 2,4,6-trichlorophenol. The organic carriers proved
flexible enough as to eliminate the need to introduce an
additional piperazine spacer between catalyst and support
as observed with modified silica. Furthermore, it has been
possible to use these polyacrylamide-supported catalysts in
a purely aqueous medium, whilst retaining a good catalytic
activity of the metallophthalocyanine complex.
These new efficient supported catalysts could easily be
used for the oxidative treatment of waste water or industrial
effluents. Another possible field of application could also
be related to the development of bleaching agents operating
at room temperature, since such catalytic systems are able
to oxidize a tannin model such as 3,5-di-tert-butylcatechol.
General Procedure for the Immobilization of the Metallophthalocy-
anines: In a typical experiment, a suspension of the metallo(chloro-
sulfonyl)phthalocyanine 1a or 1b in pyridine (20 mL) and the car-
rier was heated at reflux for 24 h. The mixture was filtered and the
solid obtained washed three times with a dimethylformamide/water
mixture (80:20, v/v) (3 ϫ 20 mL) and then ether (3 ϫ 20 mL) prior
to drying at 53 °C for 12 h. The supported metallo(sulfonami-
do)phthalocyanines were obtained as green powders. The contents
of catalyst fixed onto the carriers were determined indirectly by
calculating the amount of unchanged 1 using UV/Vis spectroscopy.
The quantities used and yields obtained are given in Table 4.
Table 4. Quantities and yields for the preparation of the sup-
ported metallophthalocyanines
Product
1
Support
Loading Yield
mg
µmol
g
µmol (NH) [µmol/g]
(%)
9
25.6
50.0
25.0
32.6
20.3
22.8
44.5
22.2
29.0
18.0
1.00
1.00
0.50
0.50
0.40
560
20.0
26.5
42.0
42.0
40.0
88
60
100
100
89
10a
10b
11
500
280
450
360
Experimental Section
General Remarks: The conversions of 2,4,6-trichlorophenol (TCP)
and 3,5-di-tert-butylcatechol (DTBC) were monitored by HPLC
(Waters) equipped with a µ-Bondapak C18 column using a meth-
anol/ammonium acetate buffer mixture [7:3, v/v; 50 m acetate
buffer (pH ϭ 5) acidified to pH ϭ 4 with acetic acid] with detection
at 220 nm for TCP and a methanol/water mixture (8:2, v/v) with
detection at 226 nm for DTBC. Ϫ The UV/Vis absorption spectra
were recorded with a Hewlett Packard 8452A spectrophotometer.
Met-Expansin-NH2 (2) (0.56 mmol-equiv. NH2/g) and Met-Ex-
pansin-Piperazine (3) (0.50 mmol-equiv. NH/g) copolymers were a
gift from EXPANSIA. The 3-aminopropyl-functionalized silica gel
(0.90 mmol-equiv. NH2/g) was purchased from Aldrich.[26] The re-
actants bromoacetic acid, dicyclohexylcarbodiimide and piperazine
are commercially available and were used without further purifica-
tion. 2,4,6-Trichlorophenol was obtained from Janssen and 3,5-di-
tert-butylcatechol from Aldrich. Hydrogen peroxide was supplied
12
General Procedure for Catalytic TCP Degradation: In a typical ex-
periment, for a catalyst/TCP ratio of 2 mol-%, 0.16 µmol of FeIII
or CoII of the supported catalyst [i.e., 8.0 mg of 9 (loading
20.0 µmol/g), 6.0 mg of 10a (loading 26.5 µmol/g), 3.8 mg of 10b
(loading 42.0 µmol/g), 3.8 mg of 11 (loading 42.0 µmol/g), 4.0 mg
of 12 (loading 40.0 µmol/g)] and 40 µL of a 1.2  aqueous solution
of hydrogen peroxide (48.0 µmol) were added to a 1 m TCP solu-
tion (8 mL, 8.0 µmol) in phosphate buffer 50 m (pH ϭ 7). The
reaction mixture was stirred at room temperature and analyzed by
HPLC. For the experiments carried out in the presence of an or-
ganic co-solvent, a 1 m TCP solution was prepared in a mixture
of 50 m phosphate buffer/ethanol or acetone (80:20, v/v). Run 7
in Table 1 was carried out with a 1 m TCP aqueous solution ad-
justed to pH ϭ 7 with NaOH (final concentration of NaOH:
1 m). When KHSO5 was used as oxidant, a solution of Curox
(12.3 mg, 40.0 µmol) in water (100 µL) was added to the reaction
mixture.
from Acros as
a
35 wt-% aqueous solution. Curox
(2KHSO5·KHSO4·K2SO4) was a gift from Peroxid Chemie GmbH.
All solvents used were of analytical grade and milliQ-water was
always used to prepare aqueous solutions. Iron(III) and cobalt(II)
tetrasulfophthalocyanines (4b and 4c) were prepared according to
previously published modifications[7a] of the method of Weber
and Busch.[27]
1H NMR Analysis of the Degradation Products of TCP by the Cata-
lytic 10a/H2O2 System: The supported catalyst 10a (loading
26.5 µmol/g) (60.0 mg, 1.6 µmol) and 400 µL of a 1.2  aqueous
solution of hydrogen peroxide (480.0 µmol) were added to a 1 m
Attachment of the Piperazine Linker on Silica: A solution of di-
cyclohexylcarbodiimide (0.56 g, 2.70 mmol) in CH2Cl2 (10 mL) was TCP solution (80 mL, 80.0 µmol) in a 50 m phosphate buffer
added dropwise at 0 °C to a solution of bromoacetic acid (0.75 g, (pH ϭ 7)/ethanol (80:20, v/v) mixture. The reaction mixture was
5.40 mmol) in CH2Cl2 (10 mL). The solution was allowed to warm stirred for 1 h at room temperature. After filtration of the sup-
to room temperature and stirred for 1 h. The dicyclohexylurea pre- ported catalyst 10a and several washings with acetonitrile, the reac-
cipitate that formed was removed by filtration, the solid was tion mixture was dried under vacuum. Then 7 mL of 1  HCl, sat-
washed three times with CH2Cl2 (3 ϫ 20 mL), and the washings urated with NaCl, was added to the dry residue and the organic
were combined. The bromoacetic anhydride solution thus obtained
products were extracted with diethyl ether (3 ϫ 60 mL). After con-
was directly added to the commercially available silica containing centration of the ether extracts, the solid residue was dissolved in
primary amine linkers (1.00 g, 0.90 mmol of NH2 functions) and
stirred for 12 h at room temperature. The modified silica was fil-
tered, washed three times with CH2Cl2 (3 ϫ 20 mL), and dried for to quantify the oxidation products. Ϫ H NMR ([D6]DMSO): δ ϭ
deuterated dimethyl sulfoxide ([D6]DMSO) for NMR analysis.
Then 5 µL of CHCl3 (62.0 µmol) was added as an internal standard
1
Eur. J. Inorg. Chem. 2001, 1775Ϫ1783
1781

M. Sanchez, N. Chap, J.-B. Cazaux, B. Meunier
FULL PAPER
6.39 (s, 2 H, maleic acid, 4%), 6.69 (s, 1 H, chloromaleic acid, 12%),
(20 µL, 8.0 µmol) in acetonitrile and 40 µL of a 1.2  aqueous solu-
6.74 (s, 2 H, fumaric acid, 3%), 7.30 (s, 1 H, chlorofumaric acid, tion of H2O2 (48.0 µmol) were then added to the reaction mixture
3%), 7.80Ϫ8.10 (br, 2 H, coupling products, 6%). Ϫ It should be every 30 min. The DTBC conversion was monitored by HPLC ana-
noted that these yields differ from one experiment to another, de- lysis.
pending on the time the oxidation reaction was stopped.
General Procedure for Catalytic DTBC Degradation: In a typical
Acknowledgments
The financial support of CNRS and Expansia is gratefully acknow-
ledged.
experiment, for a catalyst/TCP ratio of 2 mol-%, 8.0 mg of the sup-
ported catalyst 9 (loading 20.0 µmol/g) (0.16 µmol) and 40 µL of a
1.2  aqueous solution of hydrogen peroxide (48.0 µmol) were ad-
ded to a 1 m DTBC solution (8 mL, 8.0 µmol) in a 50 m borate
buffer (pH ϭ 9)/acetonitrile (1:1, v/v) mixture or in 50 m phos-
phate buffer (pH ϭ 7)/acetonitrile (1:1, v/v) or in water/acetonitrile
(1:1, v/v). The reaction mixture was stirred at room temperature
and analyzed by HPLC.
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